Vacuum switch with magnetically controllable arc

ABSTRACT

A vacuum switch has at least two electrodes situated in an evacuable insulating housing hermetically sealed by end plates. The electrodes are coaxially positioned and are movable relative to one another. At the ends of their shafts facing each other, the electrodes comprise annular or cylindrically shaped main contact parts and spiral helically shaped spark contact parts which enclose the contact parts and consist of material of good electrical conductivity. The spark contact parts are affixed to a carrier comprising an outer annular disc of material of poor electrical conductivity. An inner annular disc of material of good electrical conductivity is fitted tightly into the outer disc. The distance and thickness of the turns of the spirals or helices of the spark contact parts are dimensioned so that the ratio of distance to thickness is 1:2 to 1:10.

[ June 19, 1973 VACUUM SWITCH 'WITH MAGNETICALLY CONTROLLABLE ARC Inventors: Wilfried Kuhl,

- Gross-Schwarzenlohe; Leonhard Klug, Numberg, all of Germany [73] Assignee: Siemens Aktiengesells chait, Berlin and Munich, Germany [22] Filed: Oct. 1, 1971 [21] Appl. No; 185,666

[30] Foreign Application Priority Data Oct. 2, 1970 Germany P 20 48 506.7

[52] US. Cl. 200/144 B [51] Int. Cl. H01b 33/66 [58] Field of Search 200/144 B [56] References Cited UNITED STATES PATENTS 3,210,505, i0/1.9 65 Porter 200 144 B 3,2ll,866 "IO/I965 'Crouchet al. 200/144 B 3,366,762 .l/l968 Smith, Jr..' 200/144 B 3,509,404 4/1970 Rich.. 200/144 B I FOREIGN PATENTS OR APPLICATIONS 197,714 9 1967; U.S.S.R.... .L 200/144 B 451,286 5/1968 Switzerland 200/144 B Primary ExaminerRobert S. Macon v Attorney-Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [57] ABSTRACT A vacuum switch has at least two electrodes situated in an evacuable insulating housing hermetically sealed by end plates. The electrodes are coaxially positioned and are movable relative to one another. At the ends of their shafts facing each other, the electrodes comprise annular or cylindrically shaped main contact parts and spiral helically shaped spark contact parts which enclose the contact parts and consist of material of good electrical conductivity. The spark contact parts are affixed to a carrier comprising an outer annular disc of material of poor electrical conductivity. An inner annular disc of material of good electrical conductivity is fitted tightly into the outer disc. The distance and thickness of the turns of the spirals or helices of the spark contact parts are dimensioned so that the ratio of distance to thickness is 1:2 to l:I0.

7 Claims, 6 Drawing Figures male 2m Patented June 19, 1973 2 Sheets-Smut 2 Lbb LT a VACUUM SWITCH WITH MAGNETICALLY CONTROLLABLE ARC The invention relates to a vacuum switch. More particularly, the invention relates to at least two electrodes situated in an evacuable insulating housing, hermetically sealed by means of end plates. The electrodes are coaxially positioned and are movable relative to each other. The ends of the electrode shafts which face each other are provided with annularly or cylindrically shaped main contact parts and spark contact parts,

shaped in the form of spirals or helices. The spark contact parts enclose the main contact parts and comprise material having good electrical conductivity. Magnetic means are provided to shift a high current light arc from the main contact parts to the spark contact parts at a travelling speed.

It is known to utilize the effect of magnetic fields in order to support the quenching properties of vacuum switches. The magnetic fields may be produced by the light are current or by external circuits. It is also known to protect switch contacts by dividing them into main contacts and spark contacts. A known type of power switch or circuit breaker comprises main contact parts and annular spark contact parts. The arc, pulled between the arcing rings, rotates within a cooling agent under the action 'of the magnetic fields of the two coils through which the arc current passes in opposite directions. Each coil is defined as a flat spiral when the switch is closed,'the main contact part being situated in the center and the arcing ring being situated at the periphery of the spiral. In the known switch, the coils have a slightly arched or cambered shape when the switch is opened and their concave sides face each other. This known contact requires a great contact travel, however. During the closing of the switch, the outer rings contact each other, first of all. The outer rings may therefore become fused or welded whenthe known contact device is used, and may require an antifusion supplement or component.

Another vacuum switch with electrodes is known which comprises adjacent first and second electrode regions of variable conductivity. Slots are provided in the contacts for moving the roots of a high-current light arc. The slots extend from the circumference of each .contact disc of the second electrode region, toward the inside. The slots are generally spiral shaped and terminate at the circumference of the contact disc of the first electrode region. The slots form segments in the contact disc. The outside ends of the segments may become bent during high accelerations of the switching process, or due to dynamic current power when the high current is disconnected. This shortens the switch ing distance of the contact during the open position of 'the switch, so that sparkovers or arcovers may occur at this location.

An object of the invention is to avoid the disadvantages of the known switches and to devise for the known vacuum switches a type of contact that would make it possible to rotate the are at greater speed under the action of larger radial magnetic fields and to obtain a speedier condensation of the metal vapors and a "faster resoliditication of the switching path.

Still another object of the invention is to provide a vacuum switch which functions with efficiency, effectiveness and reliability.

To accomplish this and in accordance with the invention, the spiral or helically shaped spark contact parts are positioned on a carrier of poor electrically conducting material and the distance and thickness of the turns of the spirals or helices of the spark contact parts are so dimensioned that the ratio of distance to thickness is 1:2 to 1:10.

The carrier may be so constructed, for example, that it comprises an outer annular disc of poor electrically conducting material having an inner annular disc of good electrically conducting material fitted tightly into the outer disc. The outer diameter of the inner annular disc is so dimensioned that it has contact with the inner portion of the spiral of the spark contact part extending from the inside to the outside.

In order to provide the movable electrode with the smallest possible mass, the electrode shaft of the movable electrode to which the main contact part is affixed is preferably arranged in movable relation in a tube of good electrically conducting material, the tube being guided through the lower end plate and affixed to the lower end plate. The electrode shaft is electrically connected to the tube, at least at one spot, and the inner annular disc of the carrier for the spark contact part is affixed to the upper end of the tube, 50 that the spirally shaped spark contact part encloses the main contact part.

The cross-section, of the turns of the spirals of the spark contact part may be trapezoidal, for example, and may be reduced or decreased from turn to turn, from the inside toward the outside. The cross-section of the turns of the spirals of the spark contact part may also be ellipsoidal, forexample.

When helical spark contact parts are utilized, it is preferred to mount them on the inner wall of a cylindricalcarrier of poor electrical conductivity which is affixed to the outer circumference of the annular main contact part of the stationary electrode, so that the cylindrical main contact part of the movable electrode and the main contact part of the stationary electrode are concentrically enclosed by the helical spark contact part. In accordance with another feature of the invention, a cylindrical carrier may be provided at the main contact part of the movable electrode and an additional helical spark contact part may be mounted on the carrier so that the helical spark contact parts of the movable and stationary electrode face each other concentrically. The helices of both spark contact parts must have the same turn direction.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view of an embodiment of the vacuum switch of the invention;

FIG. 2 is a longitudinal sectional view of an embodiment of the switch of the invention having trapezoidal spark contact parts;

FIG. 3 is a longitudinal sectional view of an embodiment of an electrode of the switch of the invention having an ellipsoidal contact part; 1

FIG. 4 is a longitudinal sectional view of an embodiment of the electrodesof the switch of the invention having helical or spiral spark'contact parts;

FIG. 5 is a longitudinal sectional view of another embodiment of the electrodes of the switch of the invention having helical or spiral spark contact parts; and

FIG. 6 is a longitudinal sectional view of still another embodiment of the electrodes of the switch of the in vention having helical or spiral spark contact parts.

I 2b are connected to metal pressure parts 3a and 3b,

respectively, which fit the insulating vessel 1, with respect to the expansion coefficient. Each electrode is guided centrally and vacuum-tight through a eorresponding one of the end plates 2a and 2b. One electrode 4 is stationary and the other electrode 5 is movable.

The electrodes 4 and 5 are coaxially positioned and are movable relative to each other. The electrode shaft 6 functions as a current supply for the stationary electrode 4 and is provided at one end with an annular main contact part 7a which is enclosed by a spiral spark contact part 8a. The main contact part 70 may comprise a copper-bismouth alloy or a tungsten-copper alloy. The spiral-shaped spark contact part 80, which comprises copper, for example, is affixed to a carrier 9a.

The carrier 9a is constructed of an outer annular disc 10a of poorelectrically conductive materialsuch as, for example, noble steel, and has an inner annular disc 11a madeof good electrically conductive material such as, for example, copper, tightly fitted into the outer disc. The annular-disc 11a is affixed to the electrode shaft 6 above the main contact part 7a. The outer diameter of the inner annular disc 11a is so dimensioned that the inner area of the, spiral or helix of the spirally or helicallyshaped spark contact part 8a extending from the inside to the outside, is in electrical contact with said inner annular disc 11a. The turn distance B of the individual .turns of the spirals of the spark contact part 8a is 2 mm and the turn thickness H is 12 mm. The ratio of distance to thickness BzI-I is thus 1:6.

The movable electrode 5 is of similar structure to that of the stationary electrode 4, except for the difference that the carrier 9b with the spiral-shaped spark electrode 8b, is not affixed directly to the electrode shaft 12, but is affixed at the upper end of a tube 13. The tube 13 comprises copper, for example, and is guided through the lower end plate 2b, to which it is attached. The electrode shaft 12 is guided in movable re-' lation through the tube 13. This provides the movable electrode 5 with a slight mass.

The electrode shaft 12 is in electrical contact with the tube 13, via contact means 14 and 15, which comprise, for example, copper leads and copper pieces. The movable electrode 5 may be movedby the expansion of a metal bellows 16 whose upper end is situated at the lower end of the tube 13'. A shield or screen 17 protects the vessel 1 against metal vaporization. A double arrow 18 illustrates'the direction of movement of the movable electrode 5.

The cross-section of the turns of the spiral-shaped spark contact part depends upon the maximum switching current and should not be less than 0.5 cm for 10 kA, for example. The number of turns for the spiral or are is urged or pressed radially toward the outside by a magnetic field or loop 19, and reaches the spiralshaped spark contact parts 8a and 8b which are positioned opposite each other at a fixed distance or space, depending upon the applied rated voltage. The spirals 8a and 8b, when viewed in axial direction, turn in the same direction. The spirals 8a and 8b produce an additional magnetic field during the flow of light are current, which drives the arc along the spirals due to the resulting force component.

The dimensioning of the spiral according to the invention provides a more rapid resolidification of the switching distance or path, compared to flat contact discs. The metal vapors released by the light are may condense rapidly in the gaps between the individual turns of the spirals. In addition, the rapid resolidification of the switching distance may be improved by a slight decrease of the height of the outer turn of the spiral, with respect to the inner turn.

FIG. 2 shows the stationary electrode 4 and the movable electrode 5 with spiral-shaped spark contact parts 8, wherein the cross-section of the turns of the spirals is trapezoidal and decreases from the inside to the outside. As in FIG. 1, the annular main contact parts 7a and 7b, and the outer annular discs 10a and 10b and the inner annular discs 11a and 11b of the carriers 9a and 9b, are shown. The spark contact part 8b of the movable electrode 5 is affixed to the upper end of the tube 13, as in FIG. 1.

FIG. 3 shows the stationary electrode 4 with a spiralshaped spark contact part 8a having a cross-section of the turns of the spiral which is ellipsoidal in shape. The spark contact part 8a is affixed to the carrier 90, which comprises the outer annular disc 10a and the inner annular disc 11a, enclosing the main contact part 7a.

FIGS. 4, 5 and 6 illustrate other embodiments of the invention. In FIGS. 4, 5 and 6, the movable and stationary electrodes are illustrated in longitudinal section. In the embodiment of FIG. 4, the main contact part 7a of the stationary electrode 4 is of annular configuration and is affixed to the end or base of the electrode shaft 6.

The main contact part 22 of the movable electrode 5 is predominantly cylindrical in contrast to the main contact part 7a of the stationary electrode 4, so that the electrode shaft 12 of the movable electrode 5 is enclosed almost along its entire length by the cylindrical housing. Affixed to the outer circumference of the annular main contact part 7a of the stationary electrode 4, is a cylindrical carrier 21 of poor electrically conductive material such as, for example, noble steel. A helical spark contact part 20 is situated on the inside or inner wall of the carrier 21 in such a manner that it concentrically encloses the main contact parts 7 and 22.

At high switching currents, the light are L is driven by the magnet field or loop 19 radially outward and is guided onto the helix of the spark contact part 20. The light are current generates in the helix a magnetic field whoseforce component rotates the light are L around the predominantly cylindrical main contact part 22. At the same time, the light are L follows the shape of the helix, in axial direction. As a result, a larger surfaces becomes available for the light arc.

The embodiment of FIG. 5 differs from the embodiment of FIG. 4 in that the cylindrically shaped main contact part 22 of the movable electrode 5 encloses only a small part of the electrode shaft 12. Otherwise,

the structure of FIG. 5 is the same as that of FIG. 4. The light are L is driven radially outward by the magnetic field or loop 19 and is guided onto the helix or spiral of the spark contact part 20 and rotated around the main contact part 22.

FIG. 6 shows another embodiment of the invention, which is a modification of FIG. 4. A hollow cylinder 23 of, for example, noble steel, is embedded into the main contact part 22 andits outer surface is provided with a second helix or spiral 24. The electrode shaft 12 of the electrode 5 is enclosed almost along its entire length by the helix 24. The remaining structure of FIG. 5 is the same as that of FIG. 4.

Both spirals 20 and 24 face each other concentrically and have the same turn direction. The'turn direction may be, as desired, either clockwise or counterclockwise, since the are L is always driven downward, from theonset'of firing, independent of the direction of the current flow. The aforedescribed dimensioning rule applies to the dimensioning of the helices. That is, the helices are dimensioned so that the ratio of turn distance B to turn thicknessH, or B:I-I, is 1:2 to 1:10.

7 While the inventionhas been described by means of specific examples and in specific embodiments, we do not wish 'to be limited "thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

[We claim I 1.-A vacuum switch comprising an evacu'able insulated housinghermetica lly sealed by end plates, at least two electrodes coaxially positioned in the housing in movable relation to each other, each of the electrodes having an electrode shaft having an end facing the end of the other in the housing, a pair of a'nnularly shaped main contact parts each affixed to theend of a corresponding-one of .the electrode shafts inthe housing, a I

pair'ofhelic'ally shaped spark contactparts each enclosing a corresponding one-of the main contact parts, each of the spark contact parts comprising material having good electrical conductivity, magnetic means including the main contact parts for shifting a high current light arc from them'ain-contact parts to the spark contact parts at travelling speed, and a pair of carriers comprising a material of poor electrical conductivity eachaffixed ,to a corresponding oneof the electrode shafts and each supportingacorresponding one of the spark contact parts, and-each of the helices of the spark contactparts having turns of a thickness along aline parallel to the axis of the electrode shaft and a distance between adjacent turns dimensioned to provide a distance, to thickness ratio of 1:2 to 1:10.

2. A vacuum switch as claimed in claim 1, wherein each of the carriers comprises an outer annular disc of material of poor electrical conductivity and an inner annular disc of good electrical conductivity tightly coaxially fitted into the outer annular disc, the inner annular disc having dimensions which position it in electrical contact with the inner area of the spark contact part which extends from the inside toward the outside. 3. A vacuum switch as claimed in claim 1, wherein the cross-section of each turn of the helix of the spark contact part is of trapezoidal configuration .and the cross-sectional area of each turn decreases from turn to turn from inside to' outside.

4. A vacuurn switch as claimed in claim 1, wherein p sponding to the one of the electrodes, and further comprising means mounting the spark contact part corresponding to the'oneof the electrodes to the inner wall .......of the one of the carriers whereby the main contact part of the otherelectrode-and the main contact part of the one of the-electrodes are concentrically enclosed by the spark contact part of the one of the electrodes 6. A vacuum switch as claimed in claim 5, further comprising a tube of good electrically conductive material extending through and affixed to one of the end plates of the housing, means for movably mounting the electrode shaft of the other of the electrodes in the tube, means -for electrically connecting the electrode shaft of the other of the electrodes to the tube at at least one area, and means affixing the inner annular disc of one of the carriers to the end of the tube in the housing whereby the corresponding one of the spark contact parts encloses the corresponding one of the main contact parts. i

7. A vacuum switch as claimed in claim 6, wherein the other of the carriers'comprises a hollow cylindrical member affixed to the main contact part of the electrode shaft of the other of the electrodes, and further comprising means mounting one of the spark contact parts corresponding to the other of the electrodes to the'outer wall of the other of the carriers whereby the spark contact parts of both electrodes are concentrically positioned facing each other with the spirals thereof having the same turn direction. 

1. A vacuum switch comprising an evacuable insulated housing hermetically sealed by end plates, at least two electrodes coaxially positioned in the housing in movable relation to each other, each of the electrodes having an electrode shaft having an end facing the end of the other in the housing, a pair of annularly shaped main contact parts each affixed to the end of a corresponding one of the electrode shafts in the housing, a pair of helically shaped spark contact parts each enclosing a corresponding one of the main contact parts, each of the spark contact parts comprising material having good electrical conductivity, magnetic means including the main contact parts for shifting a high current light arc from the main contact parts to the spark contact parts at travelling speed, and a pair of carriers comprising a material of poor electrical conductivity each affixed to a corresponding one of the electrode shafts and each supporting a corresponding one of the spark contact parts, and each of the helices of the spark contact parts having turns of a thickness along a line parallel to the axis of the electrode shaft and a distance between adjacent turns dimensioned to provide a distance to thickness ratio of 1:2 to 1:10.
 2. A vacuum switch as claimed in claim 1, wherein each of the carriers comprises an outer annular disc of material of poor electrical conductivity and an inner annular disc of good electrical conductivity tightly coaxially fitted into the outer annular disc, the inner annular disc having dimensions which position it in electrical contact with the inner area of the spark contact part which extends from the inside toward the outside.
 3. A vacuum switch as claimed in claim 1, wherein the cross-section of each turn of the helix of the spark contact part is of trapezoidal configuration and the cross-sectional area of each turn decreases from turn to turn from inside to outside.
 4. A vacuum switch as claimed in claim 1, wherein the cross-section of each turn of the helix of the spark contact part is of ellipsoidal configuration.
 5. A vacuum switch as claimed in claim 1, further comprising means mounting the electrode shaft of one of the electrodes stationarily in the housing, wherein one of the carriers comprises a hollow cylindrical member of poor electrical conductivity coaxially affixed to the outer circumference of the main contact part corresponding to the one of the electrodes, and further comprising means mounting the spark contact part corresponding to the one of the electrodes to the inner wall of the one of the carriers whereby the main contact part of the other electrode and the main contact part of the one of the electrodes are concentrically enclosed by the spark contact part of the one of the electrodeS.
 6. A vacuum switch as claimed in claim 5, further comprising a tube of good electrically conductive material extending through and affixed to one of the end plates of the housing, means for movably mounting the electrode shaft of the other of the electrodes in the tube, means for electrically connecting the electrode shaft of the other of the electrodes to the tube at at least one area, and means affixing the inner annular disc of one of the carriers to the end of the tube in the housing whereby the corresponding one of the spark contact parts encloses the corresponding one of the main contact parts.
 7. A vacuum switch as claimed in claim 6, wherein the other of the carriers comprises a hollow cylindrical member affixed to the main contact part of the electrode shaft of the other of the electrodes, and further comprising means mounting one of the spark contact parts corresponding to the other of the electrodes to the outer wall of the other of the carriers whereby the spark contact parts of both electrodes are concentrically positioned facing each other with the spirals thereof having the same turn direction. 